Battery charging system



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BATTERY CHARGINGl SYSTEM Filed Nov. l5, 1940 Mardi '10, 1942.

Patented Mar. 10, 1942 BATTERY CHARGING SYSTEM Guy Bellows, Jr., Erie, Pa., assignor to General Electric Company, a corporation oi New York,

Application November 13, 1940, Serial No. 365,514

' 8 Claims. (Cln 171-314) My invention relates to battery charging systems and has for its object simple and reliable means for automatically connecting the charging generator to the battery in response to the voltage of the generator and for disconnecting the generator in response to a discharge current;

In carrying out my invention in one form, I provide a relay for controlling the operating coil of the battery charging switch, this/relay being provided with three core legs and having an armature on the middle leg biased by a spring into engagement with one of the outer legs whereby the relay contacts are separated and the charging switch maintained open. On the two outer legs are voltage coils while on the middle leg is a series coil in the battery charging circuit which coil operates upon reverse current to cause the armature to move to its biased position and thereafter assist the spring in holding the armature in that position.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a diagrammatic view of a battery charging system embodying my invention, Fig. 2 is a plan view showing details of the control relay, while Fig. 3 is a fragmentary view showing details of construction.

Referring to the drawing in one form of my invention the normally open charging switch i has its operating coil Il controlled by a relay provided with an IIE-shaped core having two outer legs I2 and I3 and a middle leg It. On the middle .leg I4 is pivotally mounted an armature I5 which is biased by a compression spring i@ :in a clockwise direction so that its right-hand end, as seen in Fig. l, is normally in engagement with the leg I3. 0n the middle leg I4 'is a series coil Il connected in the charging circuit with the switch Ill. On the leg I3 is a differential voltage coil I8 connected across the switch I0 and on the leg I2 is a voltage coil I9 connected across the charging generator 20.

The armature I5 carries on its right-hand end,

as shown, a movable contact 22 arranged to engage a stationary contactZI when the armature is moved counter-clockwise about its central pivot to bring its left-hand end into engagement with the leg I2. This engagement of the contacts 2l and 22 connects the operating coil II across the generator 20 whereupon the coil II closes lthe switch I0 which connects the charging generator 20 to the battery 23.

In the operation of the relay the shunt coil I9 generates a flux which is proportionate to the `generator voltage and flows through the bottom the relay to pick up.

core leg 24 through the cores I3 and I4 in parallel with each other and then through the armature I5 and back to the core I2, the ux dividing in the cores I3 and I4 in proportion to the relative air gaps or magnetic reluctances oi these cores.

The component of the shunt linx from the coil` I9 in the core I4 applies a counterclockwise force to the armature I5, i. e., in a circuit-closing direction, whereas the portion of the shunt flux in the core I3 applies a circuit-opening force to the armature and tends to hold the armature sealed against the end of the core I3 as shown in the v drawing.

When the generator voltage is less than the battery voltage, the switch Iii at that time of course being open, the differential coil I8 sets up a magnetic flux in the core I3 in the same direction as the component of the shunt winding flux in that core. In other words, at this time the differential coil assists the shunt flux ln holding the armature sealed against the core I3. The division of ux between the cores I3 and I4 is so arranged by adjustment of the air gaps and hence reluctances of these cores that the shunt coil cannot pick up the armature so long as there is a differential voltage applied to the coil I8 in a direction to assist the shunt flux. Also, the adjustment is such that when the generator voltage exactly equals the battery voltage and consequently no voltage is applied to the coil I8, the armature is still held sealed against the core I3 by the shunt flux in that core. However, when the generator voltage increases to a value slightly above the battery voltage, the switch I0 still being open, the coil Iii will huclr with its reversed flux the shunt iluir in the core I3 to such an extent that the holding force on the armature is overcome and the armature is moved into engagement with the core I2 to close the circuit. For example, the relay may be calibrated so that its contacts will close when the generator voltage is one and one-half volts higher than the voltage of the battery. It is contemplated that the generator will be driven at a variable speed, for example, from the axle or a railway vehicle, the voltage of the generator of course increasing with increasing speed up to the maximum voltage of the generator.

By varying the relative reluctances of the cores I3 and I4, which is done conveniently by varying the air gaps between the cores I3 and I4 and the magnetic arm 24, the amount of shunt ux in the core I3 may be changed to vary the amount of opposing ditierential ux required to cause As shown, shims Ila and assuming that the switch Ila, made of a suitable non-magnetic material such as brass, are provided between these cores and the member 2l. air gap ratio between the cores I3 and Il does not affect the drop-out or circuit-openingcharacteristics of the relay. This drop-out setting can be adjusted by means of an adjusting screw 21a extending through the armature I! in position to engage the end of the core I2 when the' armature is picked up. This screw is made of a non-magnetic material such as brass or stainless steel. y

'I'he series coil I'I is connected in the charging circuit in such direction that when the generator is charging the battery, the series coil sets up a magnetic flux in a direction to assist the coil I9 in holding the armature in its picked-up position. 'Ihe iiux throughy the series coil is mainly through the legs I2 and I4 because of the air gap at this time between the armature and the core I3.

In the event of a reversal of current flow in the generator circuit, the relay contacts and the switch I being closed, such as might be caused by decreased speed and voltage of the generator, the series coil reverses and opposes the shunt coil I9. Upon a predetermined value of reversed current, the net holding force on the amature is reduced to such a low value that the spring I8 snaps the armature back to its open position sh'own in the drawing. This deenergizes the coil I I and the switch I0 opens to open the charging circuit.

An important feature of this device is that in the event of a reversed current or battery discharge current of high value, such as might be caused by a reversed polarity of the generator, the reversed current, after effecting the release of the armature and its movement to its open-circuit position, thereafter applies a magnetic force, I0 should remain closed, to the armature, tending to hold the armature in its open-circuit position. The series ux then is mainly through the circuit formed by the legs I3 and I4. Thus if the holding force of the series coil on the armature were not reversed upon movement of the armature to its open-circuit position, its force might increase to Any such change in the such a high value during the short interval required for the switch III to open as to overpower the coil I9 and return the armature to its closed position. In such case the reverse current'condition would not be terminated.

Additional details of construction of the relay will be clear from Figs. 2 and 3 taken in connection with Fig. 1. The armature I5 is provided with a narrow central portion I5a which lits loosely between two projections 25 and 2B on opposite sides of the middle leg Il. It will be noted that the narrow portion I5a is formed in the armature by forming a slot 2l on each side of the armature at its center. As seen in Fig. 1, the side walls of these slots are inclined somewhat toward the left hand from the bottom edge upward so as to form a bearing' edge 28 on the left hand wall oi each slot. These two bearing edges on the side walls of the two slots are held against the left-hand sides, as seen in Fig. i, of the projections 25 and 2d by the pressure exerted by the spring iii.

As shown, the spring has its lower right-hand end bearing against a bracket 2d secured to the top or the armature. The other end of the spring bears against an adjustable bolt il@ which is threaded and passes through a threaded hole in till a bracket 3l. 'l'his bracket 3| is substantially U-shaped with its two'arms in substantially horizontal positions as seen in Fig-1 and secured centrally to the tops of the projections 25 and 26. The base portion IIa of the bracket is bent upward and over toward the right-hand so as to direct the spring pressure against the bracket 29. On their ends the arms of the bracket carry a. cross plate 32 made of electrically insulating material to which is secured a flexible contact arm 33 bearing the stationary contact 2l.

For purposes oi stabilization and calibration, I have shown a resistance 3l connected in circuit with the shunt coil I9. By means of an interlock switch 35 connected to and operated by the coil il, the right-hand portion of this resistance is short-circuited. This permits -an increased energization of the shunt winding until the switch Il is closed, at which time the switch 35 is opened and the entire resistance 3l inserted in the circuit with the shunt coil. This insertion of the resistance decreases the excitation of the shunt coil and consequently causes the armature to be released at a lower value o'f reversed series con excitation. f

Also, I have shown one terminalof theliiierential coil Il connected through a conductor 3B to an intermediate point on the resistor 34, whereby when the switch I0 closes the difierential coil is connected in series with the section 31 of the resistance.' The voltage across the resistance section maintains a current of low value in the diierential coil in a direction to product a iiux in the core I3 in the same direction as the shunt coil flux in the core I3. Consequently, the dinerential coil is ready to establish a seal between the core .I3 and the amature as soon as vthe relay drops out. This avoids the inductive lag otherwise required to build up a dierential coil current 'after the relay has dropped out. In other words, the small amount of flux set up by the differential coil just before the switch Il closes is reversed aftery switch Il is closed by the energization of the diierential coil by the voltage across the resistor section 31.

I have also found that increased stability of the relay against drop out in response to battery discharge current surges of short duration may be efIected by applying a copper ring 38 around the core I2. This copper ring is a single-turn closed-circuit conductor and tends to oppose any sudden change in the iiux in the core I2.

Preferably, the voltage of the generator is so selected that its voltage is less than the battery voltage until after the generator voltage passes the knee of the generator characteristic curve, it being understood that the generator is a shunt generator. This avoids the possibility of a generator voltage in case the switch Iii fails to close much higher than the battery voltage, whereby the reversed excitation of the differential coil might completely overcome the shunt i'iux in the core I3 and establish a Eux in the reverse direction sufficiently strong to maintain the armature at its open-circuit position as shown.

While I have shown a particular embodiment of my invention, it will be understood, cf course, that I do not to be limited thereto, since many modifications may he made and I. there icre, contemplate by the appended c te cover any such modifications as tall within the true spirit and of my invention,

Vilhat I claim as new and desire to secure by Letters Patent of the United is:

i; .a battery charging system cniprising a generator, a normally open switch for connecting said generator in a charging circuit with a battery, an operating coil for closing said switch, an E-shaped magnet core, an armature pivoted on the middle leg of said core, switching means operated by said armature for controlling said coil to open and close said switch, a spring for biasing said arrngture toward one of the outer legs'of said core, a differential voltage coil on said one outer core leg connected across said switch, a voltage coil on the second of said outer core legs connected acrosssaid generator, and a series coil in said charging circuit on the middle leg of said core, said series coil being energized to assist said voltage coil in holding said armature against the bias of said spring in position to energize said coil and close said switch during battery charging operation but lto oppose said voltage coil during battery discharging operation whereupon said armature moves in accordance with the bias oi said spring to deenergize said coil and open said switch, said series coil then assisting said spring to hold said armature in its biased position in response to discharging current in the event said switch fails to open.

2. A battery charging systemV comprising a generator, a normally open switch for connecting said generator in a charging circuit with a battery, an operating coil for closing said switch, an E-shaped magnet core, an armature pivoted on the middle leg oi said core, a stationary contact, a cooperating movable contact carried hy said armature, connections for connecting said contacts in circuit with said coil, a spring for biasing said armature into engagement with one oi' the two outer legs of said core with said mov-J able contact disengaged from said stationary contact, a difierential voltage coil on said one outer core leg connected across said switch, a voltage coil on the other of said outer core legs connected across said generator, and a series coil in said charging circuit on the middle leg of said core, said series coil being energized to assist said voltage coil in holding said contacts in engagement during charging hut to oppose said voltage coil during discharging whereupon said armature moves to separate said. contacts in accordance with the bias oi said spring, said series coil ii energized then assisting said spring to hold said armature in its biased position.

3. el battery charging system comprising a generator, a switch for controlling the connection oi said generator in a charging circuit with the battery, an @shaped magnet core, a pivot ally mounted armature for controlling said switch having its ends selectively movable into attracted positions toward the two outer legs of said core, means for biasing said armature to a first attracted position toward a iirst oi said outer legs to effect the opening of said switch, a voltage coil on the second of said outer legs responsive to the voltage ci said generator for producing a iirst flux in said second and middle legs tending to operate said armature against its bias toward said second outer leg to its second attracted position and for producing a second flux in said second and rst legs tending to hold said armature in said iirst attracted position, and a diierential voltage coil on said first outer leg connected across said switch arranged to assist said second ux when the generator Voltage is less than the voltage of the battery thereby to hold saidA armature in said first 'position but to oppose said second flux when the generator voltage exceeds the battery voltage thereby to effect lili movement of said armature against its bias by said voltage coil to its second attracted position to effect the closire of said switch for -closure of said charging circuit.

4. A battery charging system comprising a generator, a switch for connecting said generator in a charging circuit with the battery, a three-legged magnet; core, a pivotally mounted armature for controlling said switch, a spring for biasing said armtaure to a rst attracted position toward a first of said legs to open said switch, a voltage coil on a second of said legs responsive to the voltage of said generator for producing a iiux in said second and third legs tending to move said armature to its other attracted position against said spring to close said switch for closure of said charging circuit, and a series coil connected in said circuit mounted on said third leg and arranged in response to a battery discharge current to oppose said voltage coil and cause movement of said armature to said first attracted position by saidvspring to open said switch and then produce a ilus; in said third and rst legs to hold said armature in said first attracted position regardless of the value of said discharge current in the event that said discharge current reaches a high value.

5. A battery charging system comprising a generator, a switch for controlling the connec tion ci said generator in a charging circuit with a battery, a three-legged magnet core, an arman ture for. controlling said switch pivoted adjacent the middle leg of said core with its ends respectively movable into attracted positions towards the two outer legs oi said core, a spring for biasy ing said armature to a nrst attracted position toward a first `oi said outer legs for opening oi said switch, a voltage coil on the second of said outer legs responsive to the voltage oi said genu erator for producing a dus: in said second andV l middle legs tending to move said armature against said spring to its second attracted posi-- tion for closure of said switch and said charging circuit, and a series'coil connected in said chargn ing circuit mounted on said middle leg and ar ranged in response to a battery charging current to produce a flux in said second and middlefiegs to assist said voltage coil in holding said arma ture in said second attracted position 'out in response to a battery discharge current to oppose said voltage coil and cause movement ci said armature hy said spring to said first attracted position for opening oi' said charging circuit and then in the event said charging circuit remains closed lor producing a time in said middle and first legs to hold said armature in said first at tracted position regardless of the value of said discharge current.

6. A battery charging system comprising a generator, a switch for connecting said generator in a charging circuit with the battery, a three legged magnet core, a pivotally mounted arman ture for controlling said switch, a spring for biasing said armature to a ilrst attracted position toward a rst of said legs to eect the opening of said switch, a voltage coil on a second. of said legs responsive to the voltage oi said generator for producing a first flux in said second leg and the third leg tending to operate said armature against said spring toward said second leg to a second attracted position and for pro-1 ducing a second flux in said second and first legs tending to hold said armature in said first Yat tracted position, a differential voltage coil on said first leg connected across said switch arciieg..

in ifesponse to c, tetten? s nose solo volt-ege coil to cl economie oy seici sono" tnife meinst its bios totaler ieg; to its second ettocteti position onf?. ioi ptou clucing e second @un 'in solo. niet ono second iegs tending to liold seicl oinetuie in said iist ntti'ected position, cliiieiejntiol voltegecoii on iist outer leg connected ecoss saisi switch arranged to nssist scifi second :Elura when @enei'stoi: Voltage is less than the voltage of the battelry lout to oppose soil-l second flux when the generetor voltage exceeds the betten' voltage there toy to effect inoVen'ien-J of seid ormntuz'e against its loins by said voltage coil tc its second ettiectn ed position to eiiect the closure oi said switch for closure of said charging ciicuit, and e series coil connected in said charging circuit mounted on said middle leg and airanged in response to e. battery charging current to assist said "voitage coil in holding said armature in said second etti-acted position but in response to s battery discharge cuirent to oppose soicl voltage coli to cause movement of said armature by said spring to seid fiest attracted position to effect the open ci charging circuit end. in the event of since of dischoige cuirent for ponlncing cnil middle legs to nolo so ci ette y,

une in tiel voltage seeds '.-iie i nient of seid ormetuie against seid spring by soil" voltage coil for closure oi seid switch, menno i'esioonsive to the closni'e oi seid switch iol' n eigizing scifi differential coil o. direction to hold solo ennemie in seid position, and e series coil connected in seid chewing circuit mounted on seid tiiin'i leg wronged in response to e better-y discharge current to oppose seid voltege coii to effect movement of seid armature by said spring to said first position, said series coil being energized in response to continued discharge current to assist said differential coil in holding seid armature in seid first position.

GUY BELLOWS, JR. 

